Freiherr[1]Wilhelm Emmanuel von Ketteler (25 December 1811 – 13 July 1877) was a German theologian and politician who served as Bishop of Mainz. His social teachings became influential during the papacy of Leo XIII and his encyclical Rerum novarum.

Ketteler was born in Münster in Westphalia. In 1828 he finished the Matura in Brig, Switzerland far away from his home.[citation needed] He studied theology at Göttingen, Berlin, Heidelberg and Munich, and was ordained priest in 1844. He resolved to consecrate his life to maintaining the cause of the freedom of the Church from the control of the State. This brought him into collision with the civil power, an attitude which he maintained throughout a stormy and eventful life.

Ketteler was rather a man of action than a scholar, and he first distinguished himself as the deputy for District of Tecklenburg and Warendorf at the Frankfurt National Assembly,[2] a position to which he was elected in 1848, and in which he soon became noted for his decision, foresight, energy and eloquence.

In 1850 he was made bishop of Mainz, by order of the Vatican, in preference to the celebrated Professor Leopold Schmidt, of Gießen, whose Liberal sentiments were not agreeable to the Papal party. When elected, Ketteler refused to allow the students of theology in his diocese to attend lectures at Giessen, and ultimately founded an opposition seminary in the diocese of Mainz itself.

In 1861, Ketteler published a book on reconciliation between Catholics and Protestants in Germany, Freiheit, Autorität, und Kirche; in it, he proposed the founding of a prayer society "for the Reunion of Christendom".[3] Ketteler was friends with Julie von Massow, a Lutheran woman from Prussian nobility, who indeed founded such a prayer society.[4]

In 1858, Ketteler threw down the gauntlet against the State in his pamphlet on the rights of the Roman Catholic Church in Germany. In 1863 he adopted Lassalle'ssocialist views, and published his Die Arbeitfrage und das Christenthum.

When the question of papal infallibility arose, he opposed the promulgation of the dogma on the ground that such promulgation was inopportune. But after the dogma was defined, he submitted to the decrees (in August 1870).

He was the warmest opponent of the State in the Kulturkampf provoked by Prince Otto von Bismarck after the publication of the Vatican decrees, and was largely instrumental in compelling that statesman to retract the pledge he had rashly given, never to "go to Canossa."

To such an extent did Bishop von Ketteler carry his opposition, that in 1874 he forbade his clergy to take part in celebrating the anniversary of the Battle of Sedan, and declared the Rhine to be a "Catholic river."

^Regarding personal names: Freiherr was a title, before 1919, but now is regarded as part of the surname. It is translated as Baron. Before the August 1919 abolition of nobility as a separate estate, titles preceded the full name when given (Prinz Otto von Bismarck). After 1919, these titles, along with any nobiliary prefix (von, zu, etc.), could be used, but were regarded as part of the surname, and thus came after a first name (Otto Prinz von Bismarck). The feminine forms are Freifrau and Freiin.